Axial coordination of zinc and silicon phthalocyanines to silver and gold nanoparticles: an investigation of their photophysicochemical and antimicrobial behavior
- Authors: Masilela, Nkosiphile , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241818 , vital:50972 , xlink:href="https://doi.org/10.1142/S1088424613500016"
- Description: This work reports on the axial coordination of zinc phthalocyanine and bis-(1,6-hexanedithiol) silicon phthalocyanine to silver and gold nanoparticles. Red shifting of absorption spectra of the phthalocyanine complexes was observed after conjugation with the nanoparticles. An improvement in the photophysicochemical behavior and antimicrobial activity was achieved in the presence of metal nanoparticles for both complexes. A decrease in triplet lifetimes was observed for all the phthalocyanine metal nanoparticle conjugates. The Zn phthalocyanine complex gave the highest triplet and singlet oxygen quantum yield in the presence of gold nanoparticles. On the other hand, the bacterial inhibition was found to be best for the Si phthalocyanine derivative in the presence of nanoparticles compared to the Zn phthalocyanine counterpart. The highest antimicrobial activity was achieved for both conjugates against B. subtilis compared to S. aureaus both in the dark and under illumination with light.
- Full Text:
- Date Issued: 2013
Characterization and electrocatalytic behaviour of glassy carbon electrode modified with nickel nanoparticles towards amitrole detection
- Authors: Maringa, Audacity , Mugadza, Tawanda , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241793 , vital:50970 , xlink:href="https://doi.org/10.1016/j.jelechem.2013.04.022"
- Description: We report on the synthesis of Ni nanoparticles (NiNPs) and their application in electrocatalysis in comparison with nickel phthalocyanine (NiPc). UV–vis spectroscopy, powder X-ray diffraction, transmission electron microscopy and electron paramagnetic resonance were used in the characterization of NiNPs. Cyclic voltammetry and electrochemical impedance spectroscopy were used in electrocatalytic studies of amitrole on the glassy carbon electrode modified with NiNPs. The apparent and catalytic rate constants for amitrole on the NiNP-GCE were found to be 2.58 × 10−5 cm s−1 and 1.11 × 103 M−1 s−1, respectively.
- Full Text:
- Date Issued: 2013
Characterization and photophysical behavior of phthalocyanines when grafted onto silica nanoparticles
- Authors: Fashina, Adedayo , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241981 , vital:50989 , xlink:href="https://doi.org/10.1016/j.poly.2013.01.037"
- Description: This work reports on the functionalization of silica nanoparticles with zinc phthalocyanine complexes tetra-substituted non-peripherally with 4-carboxyphenoxyl and 3-carboxyphenoxyl groups. The phthalocyanine dyes have a free carboxyl group, facilitating the covalent attachment of the dyes on the silica surface via amide bond formation. The phthalocyanine functionalized silica nanoparticles showed higher fluorescence and triplet quantum yields as well as longer triplet lifetimes compared to the free phthalocyanines.
- Full Text:
- Date Issued: 2013
Effects of gold nanoparticle shape on the aggregation and fluorescence behaviour of water soluble zinc phthalocyanines
- Authors: D'Souza, Sarah , Moeno, Sharon , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232500 , vital:49997 , xlink:href="https://doi.org/10.1039/C3NJ00146F"
- Description: The absorption and fluorescence response as well as the fluorescence quantum yields and lifetimes of sulfonated phthalocyanines and alkyl carboxylic acid substituted zinc phthalocyanines in the presence of differently shaped water soluble gold nanoparticles were studied. The respective phthalocyanines are known to be highly aggregated in water, which is reported to markedly reduce the excited state lifetimes. This paper shows that in the presence of star shaped gold nanoparticles, the degree of phthalocyanine aggregation in water is greatly reduced, but the aggregation status of the phthalocyanines does not change for spherical Au nanoparticles. Since gold nanoparticles have already proven to be useful in numerous nanomedicinal and nanomedical applications, the disaggregation of phthalocyanines is an added advantage.
- Full Text:
- Date Issued: 2013
Electrospun fibers functionalized with phthalocyanine-gold nanoparticle conjugates for photocatalytic applications
- Authors: Tombe, Sekai , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193769 , vital:45394 , xlink:href="https://doi.org/10.1016/j.molcata.2013.01.033"
- Description: The heterogeneous photocatalytic activity of Zn(II) phthalocyanine-gold nanoparticle conjugates immobilized on electrospun polystyrene fibers was investigated using 4-chlorophenol and Orange G as model pollutants. The phthalocyanine-gold nanoparticle conjugates were synthesized via a ligand exchange reaction and characterized using spectroscopic and microscopic techniques. The interaction between the gold nanoparticles and phthalocyanines did not restrict the formation of excited singlet states, triplet states and hence the formation of singlet oxygen required for photocatalysis. The conjugates showed significantly higher singlet oxygen quantum yields and enhanced photocatalytic activity compared to the phthalocyanines. It was concluded that hybrid electrospun fibers provide great potential as active photocatalysts for oxidizing organic pollutants using singlet oxygen as an oxidant.
- Full Text:
- Date Issued: 2013
Fluorescence behavior of glutathione capped CdTe@ ZnS quantum dots chemically coordinated to zinc octacarboxy phthalocyanines
- Authors: Sekhosana, Kutloano E , Antunes, Edith M , Khene, Samson M , D'Souza, Sarah , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242019 , vital:50993 , xlink:href="https://doi.org/10.1016/j.jlumin.2012.11.044"
- Description: Core–shell CdTe@ZnS quantum dots capped with glutathione (CdTe@ZnS–GSH) were covalently linked to zinc octacarboxy phthalocyanine (ZnPc(COOH)8). The conjugate was characterized by UV/Vis, infrared and X-Ray photoelectron spectroscopies as well as transmission electron and atomic force microscopies. The fluorescence quantum yields of the core CdTe capped with thioglycolic acid increased upon formation of the core-shell. Upon conjugation with ZnPc(COOH)8, the fluorescence quantum yield of CdTe@ZnS–GSH decreased due to energy transfer from the latter to the Pc. The average fluorescence lifetime of the CdTe@ZnS–GSH QD also decreased upon conjugation from 26.2 to 13.3 ns.
- Full Text:
- Date Issued: 2013
Glutathione capped CdTe@ ZnS quantum dots–zinc tetracarboxy phthalocyanine conjugates
- Authors: Sekhosana, Kutloana E , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193780 , vital:45395 , xlink:href="https://doi.org/10.1016/j.poly.2013.02.060"
- Description: Conjugates of zinc tetracarboxy phthalocyanine (ZnPc(COOH)4) with CdTe@ZnS–GSH quantum dots (QDs) were synthesized and characterized by several techniques including X-ray powder diffraction and infrared spectroscopy. There was an observed decrease in both the fluorescence quantum yields and lifetimes of the quantum dots when they were linked or mixed with ZnPc(COOH)4 due to Förster resonance energy transfer (FRET). The FRET behavior of CdTe@ZnS–GSH–ZnPc(COOH)4 conjugates was compared to that of CdTe@ZnS–GSH–ZnPc(COOH)8. Higher FRET efficiencies were observed for CdTe@ZnS–GSH–ZnPc(COOH)4-mixed or CdTe@ZnS–GSH–ZnPc(COOH)4-linked compared to the corresponding CdTe@ZnS–GSH–ZnPc(COOH)8-mixed or CdTe@ZnS–GSH–ZnPc(COOH)8-linked. Also CdTe@ZnS–GSH–ZnPc(COOH)4-mixed (containing coreshell QDs) showed higher FRET efficiency than CdTE–TGA–ZnPc(COOH)4-mixed containing core QDs. The FRET efficiencies were found to be 63% and 59% for the CdTe@ZnS–GSH–ZnPc(COOH)4-linked and CdTe@ZnS–GSH–ZnPc(COOH)4-mixed samples, respectively.
- Full Text:
- Date Issued: 2013
Influence of nanoparticle materials on the photophysical behavior of phthalocyanines
- Authors: Nyokong, Tebello , Antunes, Edith M
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190450 , vital:44995 , xlink:href="https://doi.org/10.1016/j.ccr.2013.03.016"
- Description: This review presents recent data on the photophysical behavior of phthalocyanines when conjugated to quantum dots, gold and magnetic nanoparticles. In some cases such conjugates offer the possibility of being used in “combination therapy”, where two or more substances may be used for treating one disease. The review focuses on the effect that the presence of nanoparticles has on the excited and triplet state parameters of the phthalocyanines. Five tables listing these parameters are presented.
- Full Text:
- Date Issued: 2013
Nanoconjugates of CdTe@ ZnS quantum dots with cobalt tetraamino-phthalocyanine
- Authors: Adegoke, Oluwasesan , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242049 , vital:50996 , xlink:href="https://doi.org/10.1016/j.jphotochem.2013.02.010"
- Description: The covalent linking of thiol-capped CdTe@ZnS QDs with cobalt tetraamino-phthalocyanine (CoTAPc) has been successfully carried out. Several techniques such as time-resolved fluorescence measurements, thermal gravimetric analysis,transmissionelectronmicroscopy andspectrophotometric techniques were employed to characterize the nanoconjugates. Covalent binding of the QDs with CoTAPc resulted in the fluorescence quenching of the former. In the presence of varying concentrations of superoxide anion (O2 •−), the fluorescence of the QDs in the conjugate was gradually enhanced and the detection limits obtained were 2.1 and 2.4 nM for the smaller and larger QDs, respectively. Based on the excellent selectivity displayed by the nanoconjugates towards O2 •− over other biologically active species, a potential nanosensor was developed.
- Full Text:
- Date Issued: 2013
Nonlinear optical behavior of metal octaphenoxy phthalocyanines
- Authors: Sanusi, Sikiru O , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241717 , vital:50963 , xlink:href="https://doi.org/10.1142/S1088424613500715"
- Description: In this work, we investigated the nonlinear optical absorption properties of chloroaluminum, chlorogallium, chloroindium, zinc and lead octaphenoxy phthalocyanines in a dimethyl sulphoxide solution using 5 ns pulses at 532 nm. Using the Z-scan technique, the nonlinear optical properties and the excited state absorption cross-sections were determined by fitting the Z-scan data. The k value was the highest for Pb derivative at 211, making it the best nonlinear optical material. In terms of hyperpolarizability, Pb derivative (containing a larger central metal) also gave the largest value followed by aluminum derivative (containing a small central metal). The distortion of the ring caused by the central metal is used to explain the hyperpolarizability values. Large nonlinear absorption coefficient values, βeff, in the range of 3.558–4.763 × 10-9 cm.W-1 and low saturation fluence values, Fsat between 21.5–38.5 mJ.cm-2, were obtained for these samples.
- Full Text:
- Date Issued: 2013
Optical limiting analysis of phthalocyanines in polymer thin films
- Authors: Britton, Jonathan , Litwinski, Christian , Antunes, Edith M , Durmus, Mahmut , Chaukea, Vongani , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232488 , vital:49996 , xlink:href="https://doi.org/10.1080/10601325.2013.736269"
- Description: This paper reports on the effect of embedding twelve phthalocyanines containing In, Ga, Zn and Al as central metals in polymer thin films on their optical limiting abilities. This paper also examines the effect of forming a covalent link between zinc tetraamino phthalocyanine (10) and poly (methyl acrylic acid) (PMAA), and Zn (11) or OHAl (12) octacarboxy phthalocyanines with polyethylenimine (PEI). The average film thickness (for phthalocyanines mixed or linked to polymers) of each Pc/Polymer films on glass was 95 μm. The hyperpolarizability of the twelve phthalocyanines was found to be in the range of 10−26 to 10−24 esu.L. This is significantly higher than the hyperpolarizabilities of these phthalocyanines in solution, which ranged from 10−30 to 10−26 esu.L. Degradation studies seem to indicate that placing a phthalocyanine within a polymer thin film may protect it slightly from photo- and thermal degradation.
- Full Text:
- Date Issued: 2013
Oxovanadium (IV)-containing poly (styrene-co-4′-ethenyl-2-hydroxyphenylimidazole) electrospun nanofibers for the catalytic oxidation of thioanisole
- Authors: Walmsley, Ryan S , Litwinski, Christian , Antunes, Edith M , Hlangothi, Percy , Hosten, Eric C , McCleland, Cedric , Nyokong, Tebello , Torto, Nelson , Tshentu, Zenixole R
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241665 , vital:50959 , xlink:href="https://doi.org/10.1016/j.molcata.2013.07.018"
- Description: The catalytic fibers have been fabricated by the electrospinning of a copolymer of styrene and 2-(2′-hydroxy-4′-ethenylphenyl)imidazole {p(ST-co-VPIM)} followed by a reaction with a methanolic vanadyl solution to afford the oxovanadium(IV)-containing poly(styrene-co-4′-ethenyl-2-hydroxyphenylimidazole) fibers {p(ST-co-VPIM)-VO fibers}. The relationship between polymer concentration and fiber diameter was investigated, and at high concentration (20 wt%) the fibers were quite large (average diameter of 3.8 μm) but as the concentration was reduced fibers of much lower diameter were produced (0.6 μm using 8 wt%). The BET surface area for p(ST-co-VPIM) fibers (0.6 μm diameter) was 47.9 m2 g−1 and functionalization of p(ST-co-VPIM) with vanadyl resulted in an increase in surface area to 60.7 m2 g−1 for p(ST-co-VPIM)-VO. The presence of vanadyl was confirmed by XPS and EPR. The EPR spectral analyses depicted complex speciation of vanadium within these polymer supports. These catalytic fibers were applied under batch and continuous flow conditions for the catalytic oxidation of thioanisole using hydrogen peroxide. The continuous flow method gave excellent and constant conversion throughout the 10 h period studied. The leaching of vanadium from the fiber support was 4% over the 10 h period indicating a significant stability of the material.
- Full Text:
- Date Issued: 2013
Photodegradation of Orange-G using zinc octacarboxyphthalocyanine supported on Fe3O4 nanoparticles
- Authors: Modisha, Phillimon , Nyokong, Tebello , Antunes, Edith M
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241653 , vital:50958 , xlink:href="https://doi.org/10.1016/j.molcata.2013.09.030"
- Description: Zinc octacarboxy phthalocyanine (ZnOCPc) was covalently immobilized on the surface of magnetite nanoparticles (MNPs) for the photocatalytic degradation of Orange G (OG) under visible light irradiation. It is noteworthy that the catalyst can be easily recovered using an external magnet and that it is reusable. The ZnOCPc remained bound to the MNP surface even after 25 min of photolysis as confirmed by the FT-IR and X-ray diffraction spectra. Kinetic analysis shows that the photodegradation rates of OG can be approximated to be pseudo-first order, according to the Langmuir–Hinshelwood kinetics model.
- Full Text:
- Date Issued: 2013
Physicochemical properties of a zinc phthalocyanine–pyrene conjugate adsorbed onto single walled carbon nanotubes
- Authors: Ogbodu, Racheal O , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242314 , vital:51029 , xlink:href="https://doi.org/10.1039/C3DT50335F"
- Description: A conjugate between zinc monoamino phthalocyanine (ZnMAPc) and pyrene (Py) represented as ZnMAPc–Py (complex 3) was synthesized and characterized by various spectroscopic techniques and by elemental analysis. This manuscript also reports on the photochemical and photophysical properties of 3. This new compound exhibited higher triplet, fluorescence and singlet oxygen quantum yields in comparison to the phthalocyanine alone, hence showing the advantages of attaching pyrene to the Pc without breaking the conjugation. We also observed a decrease in photophysical parameters upon adsorbing the ZnMAPc–Py complex onto single walled carbon nanotubes (SWCNT). However, ZnMAPc–Py still generated some singlet oxygen when adsorbed onto SWCNT.
- Full Text:
- Date Issued: 2013
Physicochemical properties of zinc monoamino phthalocyanine conjugated to folic acid and single walled carbon nanotubes
- Authors: Ogbodu, Racheal O , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241761 , vital:50967 , xlink:href="https://doi.org/10.1016/j.poly.2013.05.025"
- Description: This study reports on the photophysical and photochemical behavior of the conjugates formed by covalent and non-covalent bonding between zinc monoamino phthalocyanine (ZnMAPc) and either single walled carbon nanotubes (SWCNTs) or folic acid (FA). The conjugates were characterized using FTIR, X-ray powder diffractometry, thermogravimetric analyses, transmission electron microscopy and Raman spectroscopy. 1H NMR and mass spectroscopies were only employed for ZnMAPc–FA conjugate. There was a slight increase in the triplet and singlet oxygen quantum yields on conjugating ZnMAPc to SWCNTs (or FA), while a decrease in the photophysical and photochemical parameters were observed upon adsorption of the ZnMAPc–FA conjugate to SWCNTs.
- Full Text:
- Date Issued: 2013
Silica nanoparticles grafted with phthalocyanines
- Authors: Fashina, Adebayo , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232545 , vital:50001 , xlink:href="https://doi.org/10.1039/C3NJ00439B"
- Description: Silica nanoparticles grafted with phthalocyanines (tetra-substituted non-peripherally with 4-carboxyphenoxy and 3-carboxyphenoxy groups) have been synthesized, characterized and their photophysical properties evaluated in solution. The phthalocyanine dyes have a free carboxyl group facilitating the covalent attachment of the dye onto the silica surface via ester bond formation. The photophysical properties of the hybrid nanoparticles show higher fluorescence and triplet quantum yields as well as longer triplet lifetimes as compared to the free phthalocyanines. The triplet quantum yields were found to be higher for the phthalocyanines with ester bonds as compared to the amide bonded linkages. The silica nanoparticles were also studied in artificial lysosomal fluid over a period of 96 h and the dissolution of the nanoparticles was monitored and confirmed using inductively coupled plasma optical emission spectrometry.
- Full Text:
- Date Issued: 2013
Synthesis and nonlinear optical examination of 3 (4), 15 (16)-Bis-(4-tert-butyl-phenoxy)-10, 22-diaminohemiporphyrazinato chloroindium
- Authors: Britton, Jonathan , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241739 , vital:50965 , xlink:href="https://doi.org/10.1016/j.molstruc.2013.05.001"
- Description: 3(4),15(16)-Bis-(4-tert-butyl-phenoxy)-10,22-diaminohemiporphyrazinato chloroindium hemiporphyrazine was synthesized from 1,3,5-triaminobenzene and 4-tert-butyl-phenoxyisoindoline. The structure of the complex was confirmed using mass, nuclear magnetic resonance and infrared spectroscopies. The nonlinear parameters of the compound was also analyzed in dimethylformamide and found to be significantly greater than previously analyzed phthalocyanines.
- Full Text:
- Date Issued: 2013
Synthesis and photophysicochemical properties of zinc phthalocyanine derivatized with benzothiazole or carbazole photosensitizers
- Authors: Khoza, Phindile , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241728 , vital:50964 , xlink:href="https://doi.org/10.1016/j.poly.2013.05.046"
- Description: The synthesis of new zinc phthalocyanine complexes containing 3-(2-benzothiazol-2-yloxy) (complex 3) and 3-(carbazol-2-yloxy) (complex 4) substituents at the non-peripheral positions are reported. The new compounds were characterized by elemental analysis, FT-IR, 1H NMR, mass spectrometry and UV–Vis spectroscopy. The effects of carbazole and benzothiazole substitutents on the photophysical and photochemical parameters of ZnPc are reported. These new phthalocyanines are non-aggregated in common solvents and show improved photophysicochemical properties. The 3-(2-benzothiazol-2-yloxy) substituted complex showed the longest triplet lifetime ever reported for a zinc phthalocyanine (1.7 ms).
- Full Text:
- Date Issued: 2013
Synthesis and photophysicochemical studies of a water soluble conjugate between folic acid and zinc tetraaminophthalocyanine
- Authors: Khoza, Phindile , Antunes, Edith M , Chen, Ji-Yao , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242142 , vital:51005 , xlink:href="https://doi.org/10.1016/j.jlumin.2012.06.048"
- Description: This work reports on the synthesis of zinc tetraaminophthalocyanine (ZnTAPc) functionalized with folic acid (FA), forming ZnTAPcFA. The conjugate between FA and ZnTAPc was soluble in water whereas ZnTAPc alone is not. The structure of ZnTAPcFA conjugate was elucidated by 1H NMR, MALDI-TOF mass and FTIR spectra. Photophysical and photochemical studies of ZnTAPcFA were conducted in DMSO. The increase in fluorescence quantum yield of the conjugate was accompanied by a decrease in the triplet and singlet oxygen quantum yields. The changes in triplet quantum and singlet oxygen quantum yields were marginal when ZnTAPc was simply mixed with FA without a chemical bond.
- Full Text:
- Date Issued: 2013
Synthesis and physicochemical behaviour of aluminium bis and tris (diammine platinum) octacarboxyphthalocyanine
- Authors: Malinga, Nduduzo , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241970 , vital:50988 , xlink:href="https://doi.org/10.1016/j.poly.2013.02.073"
- Description: Hydroxy aluminium octacarboxy phthalocyanine (Al(OH)OCPc) was conjugated with a diammine platinum complex to give conjugates containing two or three platinum complexes (represented as: Al(OH)OCPc(Pt)2 and Al(OH)OCPc(Pt)3). It was found that the complexes were soluble in water at a pH > 8.2. Both conjugates were found to have two fluorescence lifetimes. The triplet and singlet oxygen quantum yields increased for the conjugates compared to Al(OH)OCPc alone.
- Full Text:
- Date Issued: 2013